An automated continuous-flow hydride generation system was developed for the determination of trace amounts of Se ^IV and total Sb, As and Ge in sea-water using ICP-MS detection. Since the same responses can be obtained between the Sb species Sb ^V and Sb ^III , among the As species As ^V , As ^III , monomethylarsonic acid and dimethylarsinic acid, and between the Ge species Ge ^IV and monomethylgermanium, a single Sb, As and Ge species can be used for calibration. A sensitivity enhancement was observed when methanol was used for matrix modification. Matrix modification was also useful for achieving recoveries close to 100% in recovery tests performed on a sea-water sample. Detection limits of 2.2 ng l ^-1 for Sb as Sb ^III , 6.5 ng l ^-1 for As as As ^V , 2.4 ng l ^-1 for Ge as Ge ^IV and 0.5 ng l ^-1 for Se ^IV were obtained. For replicate determinations in both a standard solution and a real sea-water sample, the repeatabilities were within 7% (as RSD). The proposed method is rapid (15 samples can be analysed per hour) and sufficiently sensitive to allow trace amounts of Se ^IV and total Sb, As and Ge to be directly determined in surface sea-water samples taken at a high latitude of the North Pacific Ocean from Japan to Canada.